New, more stringent emission limits for diesel engines necessitate the use of exhaust after-treatment devices, such as diesel particulate filters. Certain after-treatment devices include a regeneration cycle. During the regeneration cycle, the temperature of the exhaust gas plume may rise significantly above acceptable temperatures normally experienced by exhaust systems without such after-treatment devices. As an example, exhaust systems without after-treatment devices typically discharge exhaust gas at a temperature of around 650 degrees Kelvin. An exhaust system having an after-treatment device that includes a regeneration cycle may experience an exhaust gas plume temperature exceeding 900 degrees Kelvin at its center core. Exhaust gas at this high exit temperature creates a potentially hazardous operating environment.
Prior art and current exhaust pipe diffusers passively feed cooling ambient air directly through the duct wall, but do not optimally intermingle the cooling air with the hot core stream in the center of the exhaust pipe. The result at the exit plane is a cool ring of exhaust flow surrounding a very hot exhaust core.
Thus, there exists a need for a flow diffuser for an exhaust pipe for diffusing hot exhaust gas on exit from an exhaust pipe.